Attempts have been made to prepare less toxic antimonials for use in chemotherapy on Schistosomiasis japonicum.It has been established^[5] that 2,3-dimercaptopropanol is a powerful antilewisite because it forms a stable ring compound (Ⅱ) with arsenic.It seems reasonable to suppose that analogous cyclic antimony mercaptides (such as IV and V) should ibe difficult to dissociate and therefore would be less toxic.